Description of the Related Art
A conventional gyroscope which produces a signal corresponding to its rotation is generally designed as shown in FIG. 2. In particular, the gyroscope comprises a mechanical vibrator resembling a tuning fork in appearance. This vibrator is activated by activating elements so that the vibrator may be constantly subjected to vibration. Thus, an inertial force is produced. The gyroscope further includes a base and detecting elements mounted to the vibrator. As the base is rotated, a force, known as the Coriolis force acts on the vibrator. This Coriolis force is detected by the detecting elements. Since the Coriolis force varies according to the angular velocity, the angular velocity of the rotation can be determined by detecting warpage of the tuning fork with piezoelectric devices, the warp being caused by the Coriolis force.
The above-described gyroscope has various drawbacks discussed as follows.
(1) Since the gyroscope responds to rectilinear acceleration as well as to angular velocity, error occurs in detecting the angular velocity. PA1 (2) The accuracy of the gyroscope is temperature dependent. Specifically, piezoelectric devices, polarized in the direction of thickness of the tuning fork, are used as the detecting elements which detect the warp of the tuning fork in the direction of thickness. Electric potential develops on the polarized surface of the tuning fork according to a temperature change by the piezoelectric effects. However, electrodes must be installed on the polarized surface in order to detect the warpage. Therefore, the signal developed across the electrodes varies with temperature. PA1 (3) The vibration which activates the tuning fork is transmitted to the piezoelectric devices. Accordingly, the vibration is detected as noise. PA1 (4) Output characteristics of the gyroscope vary greatly from apparatus to apparatus. For example, the characteristics are affected by the thickness of adhesive used to bond the piezoelectric devices to the tuning fork and also by strain. Also, as discussed the characteristics drift or are otherwise effected by temperature. PA1 (5) Numerous laborious operations are needed to manufacture the gyroscope and, therefore, it cannot be manufactured efficiently. For instance, it is difficult to adjust the resonance frequency of the tuning fork and the sensitivity. Further, it is difficult to bond the piezoelectric devices to a metal. In addition, it is difficult to electrically connect the piezoelectric devices with the circuit. PA1 (6) The accuracy of the device is poor. Especially, the error increases in the region where the angular velocity is of small magnitude.